Lidewij Vligenthart was Peter Van Houten's assistant in Amsterdam. He was often drunk and that bothered her day after day. She later resigned after realising how heartless he could be. She was the one who showed Augustus and Hazel around Amsterdam, to places such as the Anne Frank house and she had treated them to an elaborate meal in the restaurant Oranjee on their first day of visit.

Lidewij was also the one who originally forwarded Hazel and Augustus' letter to Peter Van Houten. She had done this in hopes that Peter would be inspired, give up on alcohol, and begin to write again. Lidewij only wanted Peter Van Houten to write again in hopes he would become sober.

It also says that she is paid well for her job, but resigns (as said above) because she realized that he is a heartless drunk man. Peter Van Houten also states that "(Lidewij) is exceptionally talented in the field of spending my money.” After she tells him that they (Lidewij and Van Houten) bought them dinner at Oranjee the previous night.

It appears that while she was still working for Peter Van Houten, she wanted him to recover from being an alcoholic. That is why she invited Hazel and Gus to come visit him in Amsterdam. When Peter Van Houten does not want to talk to Hazel and Gus, she tries to convince him to do so. Eventually, she gives up and quits.

Trivia

Late in the book, it is revealed Lidewij's love interest is a man named Bas.

Her email appears to be as: lidewij39@gmail.com.

It has been mentioned in the book that Lidewij is pursuing a degree in American literature.